Inhibiting boiler deposits



June 8, 1965 Filed Dec. 28, 1961 H. L. KAHLER ETAL INHIBITING BOILERDEBOSITS 4 Sheets-Sheet 1 ATTORNEYS.

June 8, 1965 KAHLER ETAL 3,188,289

INHIBITING BOILER DEPOSITS Filed D60. 28, 1961 4 Sheets-Sheet 3 SODIUMLIGNO SU LFONATE *6 C MC- SODIUM LIGNO SULFONATE DEPOSIT, Gms/Ft HIGHHEAT TRANSFER 0 I so I ga e I05 ORGANIC PPM flarzyLema )zfir ATTORNEYJ',

June 8, 1 H. 1.. KAHLER ETAL 3,188,289

INHIBITING BOILER DEPOSITS 4 Sheets-Sheet 4 Filed Dec. 28. 1961zofiifiwmzw lo E 3 w; 3 N 3 m6 000 02 mmtwzfiz. CE: :9: 0 8

ATTORN EYS United States Patent 3,183,289 nuuerrmn DEWQSETS Harry LewisKahler, Feasterville, and Ray T. Zea-by,

The present invention relates to processes and compositions forpreventing or reducing the deposits which otherwise will form in steamgenerating systems such as steam boilers, evaporators, economizers, andthe like.

The invention more particularly relates to the reduction or preventionof deposits in steam generating systems by introducing additives intothe feed water which supplies the steam generating system, or directlyinto the steam generating device itself. The invention is particularlyconcerned with the introduction of the sodium salt ofcarboxymethylcellulose either alone or with other materials.

In the drawings, FIGURE 1 is a diagrammatic illustration of a testingboiler used in the experiments according to the invention.

FIGURES 2, 3 and 4 are curves plotting deposit in grams per square footas an ordinate, against organic additive in parts per million as theabscissa in FIGURES 2 and 3 and against degree of substitution as theabscissa in FIGURE 4.

It is well known in the art that organic materials such as tannins,lignins and starches will prevent or reduce boiler deposits and modifythe condition of boiler sludges so that they can be more convenientlyeliminated by blowdown.

We have discovered that the sodium salt of carboxymethylcellulose hasremarkable properties in reducing or preventing boiler deposits on heattransfer surfaces and conditioning boiler sludges for proper removalfrom the boiler by blowdown.

The sodium salt of carboxymethylcellulose is derived from cellulose bysolubilizing the cellulose to obtain a structure symbolized by ROCHCOONa, where R represents the cellulose structure. Each anhydroglucoseunit (C H O in the cellulose structure contains three active hydroXylgroups to which carboxymethyl groups can be attached. It is the sodiumsalts of carboxymethyl groups which make the cellulose gum watersoluble. The material is described in Hercules Cellulose Gum (1956),Form 835.

Carboxymethylcellulose is usually used as a sodium salt, although otherWater soluble salts may be used, of which the potassium salt, theammonium salt, and the calcium salt are typical. The sodium salt ofcarboxymethylcellulose is for convenience abbreviated in the tables asCMC, a Hercules registered trademark.

We have also discovered that the sodium salt of carboxymethylcellulosewhen combined with an organic material of the class consisting oftannin, lignin, sult'onated lignin and thiolignin acts cooperatively tofurther reduce or prevent boiler deposits and to improve theconditioning of the sludge, having an additive effect when the sodiumsalt of carboxymethylcellulose and the organic material are usedtogether.

We have also discovered that the power of the sodium salt ofcarboxymethylcellulose to prevent boiler deposits is a function of thedegree of substitution. The degree of substitution may be defined as thenumber of available hydroxyl groups per anhydroglucose group which havecombined with carboxymethyl groups. In cellulose each anhydroglucosegroup has three hydroxyl groups which can be replaced, so that thetheoretical maximum substitution is 3, and theoretically thesubstitution can vary Patented lune 8, 1965 from O to 3. Practically,however, the substitution varies between 0.2 and 3.0 and preferablyvaries between 0.4 and 2.0. For high heat transfer, a substitution ofabout 0.7 is most eifective in reducing or preventing boiler deposits; V

We have also discovered that the power of the sodium salt ofcarboxymethylcellulose to preventor reduce boiler deposits is a functionof the length of the polymer chain,

which is the number (x) of anhydroglucose units 'in the molecule whenthe formula is written (C H 0 Polymer length has a very powerful effecton viscosity on the sodium salt of carboxymethylcellulose, the smallerchain lengths giving lower viscosity and the longer chain lengths givinghigher viscosity, the viscosity varying between the limits of 15 to40,000 centipoises for a 2% by weight solution of the water soluble saltin water.

We have determined that the sodium salt of carboxymethylcellulose isstable at high temperatures, and high pressures and on high heattransfer surfaces of steam generating systems.

The slowly swelling and viscous sodium salt of carboxymethylcellulosecan be fed into steam generating systems either as paste or in solidpowder form.

The sodium salt of carboxymethylcellulose and the combination of thesodium salt of carboxymethylcellulose and organic materials such as thetannins perform well with boiler antifoams of the character well knownin the art such as the polyamides which are condensates of amines andacids of varying length and configuration. A simple example of this typeis ethylene diamine acylated by 4 moles of a fatty acid having a carbonchain length above 10, such as oleic acid.

Another type of antifoam in general use today is the ether type made bytreating glycols at superatmospheric pressures. The general resultingcompounds can be expressed by H(OC H OH.

A third type is a modification of the second type but distinct from it.This type, well known in the art, results from interacting step-wisemixtures of ethylene glycols with propylene glycols to give a series ofproducts represented by (HO(C H (C H (C H I-I.

The sodium salt of carboxymethylcellulose and the combinations thereofwith organic material such as tannins, lignins, and the like, have beenspecifically applied to reduce or eliminate the boiler deposits causedby phosphates, hydroxy phosphates, hydroxides, and silicates which wouldotherwise cause incrustation of the character commonly encountered inboilers due to raw water or feed water.

The researches were carried out in two experimental boilers. The testingfor boiler dispersing power and deposit prevention, stability of organicmaterials and the quality of the steam was carried out in two boilers ofthe character diagrammatically illustrated in FIGURE 1. One of these twoboilers had been used in tests of this character for 12 years and theother for 9 years and the test results have been found to coordinatewell with plant operation.

The boiler 20 has a high heat transfer surface 21 and a low heattransfer surface 22 due to electric heaters. Blowdown is accomplishedthrough a blowdown line 23. The high heat transfer surface 21 transfers180,000 B.t.u. per square foot per hour, and the low heat transfersurface 22 transfers 28,000 Btu. per square foot per hour. In the laterparts of the specification and the tables when high and low heattransfer surfaces are referred to, this is what is meant.

The heaters supply the heat to run the boiler at 300 p.s.i. and 420 F.unless otherwise indicated, and they also provide the heat transfersurfaces on which the boiler dis persive power is evaluated. The boilerhas a steam leg 24.

The compartment to the left connected both through the steam and theboiler water phases is a water level control for controlling the waterlevel in the boiler. Each experiment was run two days unless otherwisestated.

At the end of each experiment the electrical heaters 21 It will beevident from Table 1 that there are differences in the power of thesodium salt of canboxy methylcellulose depending on this degree ofsubstitution, the 7 series being the most powerful and giving areduction on total and 22 were removed and the deposits thereon were eX-deposit of the-order of 70 to 80%. amined critically. Similar resultsare obtained for other water soluble The boiler operates on a syntheticfeed water as later salts of carboxymethylcell-ulose. described by whichboiler encrustants and organic treat- 'It should the noted, however, tht i 11 f the grades of ments are introduced into the boiler as needed. Aconthe sodium salt of .carboxymethylcellulose had the power tinuousblowdown system operates the boiler at 15 cycles to reduce or eliminate:boiler deposits and all had sludge of concentration. The sight glass 25above the water line conditioning properties as indicated by theturbidity of is used for the detection of foaming of the boiler water. Ath bl wdown of the boiler water. Whereas in expericontimwus recordingSodium spectrophotometer ments without the sodium salt of'carboxyme'thylcellulose Shown) is St/d On each experiment to record ySteam there was very low turbidity, the sodium salt ofeanboxycontamination above normal. methylcellulose increased theturbidity 'from 2 to 11 told.

Feed and treatmen W t r ar Obtained from a tank 25 The increase inturbidity is important as it means that through a feed Watfil' P p 7 tothe boiler. the sludges are properly conditioned and dispersed so thatSODIUM SALT OF CARBOXYMETHYLCELLULOSE they can be effectively el minatedby boiler blowdown.

FOR REDUCING BOILER DEPOSITS AND CON The illlbldlty 0f the b01181b'lOWdO VE/H 111 111658 expen- DITIONING BOILER SLUDGES ments seems tothe somewhat proportional to the boiler power of the sodium salt ofcarboxymethylcel'lulose in Table 1 shows a first series of experimentsin which relation Preventing deposits the sodlum Salt ofcarboxymetllylcellflose was used The concentration of the water solublesodium salt of forms at P 10 Parts P carboxymethylcellulose in the waterof the steam generatand Compared with test 1'unS W1thutLthe Sodium Salting equipment should be mtaintained at a level up to 100 ofcarboxymethylcellulose. It W111 be noted1 that in every ppm theconcentration being effective at an Timex The case Where the sodmm .Saltof carboxymethycenulfsa s question of what concentration is effectivedepends upon Presentthe tota1dep1tWaS much 1653 ii l an the scalingload, and on some scaling loads 3 ppm. low heat transfer surfaces andthe borer tur ldity ran or 5 ffac i much higher.

It will be noted that the effect of the sodium salt of COMBINATION OFTHE SODIUM SALT OF carboxymethylcellulose is almost as impressive on theCARBOXYMETHYLOELLULOSE AND ORGANIC high heat transfer surface as on thelow heat transfer TREATMENT SUCH AS TANNIN surface.

The numbers following the CMC indicate the degree of In eXPenmentS WaterSoluble 4 Salts of carsubstitution of the sodium salt ofcarboxymethylcellulose bPxymethylceuulosea was found that the as laterexplained, and the letters following these num- F Saltsofcflnboxymthylwllulose gave add1t{ve Power bets have the followingmeaning: in total deposit reduction and sludge dispersion when used withother organic materials such as tannin, lignin, 4O sulfonated ligriinand thiolignin. Experiments on this g g subject are reported in Tables 2and 3. mm VKSCOSIPY Table 2 shows that a small amount of the sodium saltcry Ylscoslty of carboxymethylcellulose used with a modified treatment Yas described in the footnote gave additional reduction in 1g vlscimty.deposit compared with the modified tannin treatment SM0re readilydissolved A5 alone Table 1 Table 2 BOILER EXPERIMENTS WITH CMC BOILEREXPERIMENTS, CMC+ORGANIC Total Deposit, Boiler Water, Total Deposit,Girls/it. ppm. 50 Gms/itfi Turbidity Exp. N 0. Treatment in Boiler Exp.Treatment in ppm. in p.p.m.

Water, p.p.m. Low High Tur- No. Low High SiOz Heat Heat bidity CMC Heat;Heat Trans- Transas Trans- Transicr fer 810; for fer No organic 1.205.20 9 No CMC- O 8 11 0 }30 Modified Tannins 1 0. 48 1. 16 76 10 one4M 1. 04 a. 9 25 10 7.5 CMC 7HS22.5 Modified 0.15 0.48 160 10 CMC 7AT 0.23 0.27 119 10 Tannins. 10 CMC 7LT o. 31 0. ss 94 1o 67 7.5 CM OTBS-22.5 Chestnut 0.18 0. 49 04 6O Tannin.

V 1 Modified Tannins as a combination of Quebraclio, Chestnut, Wattle wCMC 33 42 so 10 ii pg g i sftgwvc tannins secured as an extract from theleather tanning Conditions: No. 3 Boiler, 300 psi, 15 cycles ofconcentration, 3 day H testing. with a feed water of S p.p.m. Ca, 3 ppm.Mg (as CaC0 and (1:) sulhcient alkalinity, sultite and silica fed togive boiler water balances of 600 p.p.m. P alkalinity, 700 p.p.rn. Malkalinity (both as 02100:) and residuals of 20 to each of phosphate.sulllte and silica. in CMC 9H 0.41 1.0 81 1o The turbidity obtained fromthe combination treatment CMC 12H& M 72 51 10 was over twice as great asthat obtained from the modi- 7 fied tannin alone :and this indicatesthat the sludge condi- 1 All 7 grades in these experiments.

Conditions: Experimental Boiler No. 2, 300 p.s.i., 15 cycles ofconcentration using a feed water 01'18 p.p.m.-Ca, 9 p.p.m. Mg (both asCaCO3) with sutficient alkalinity, phosphate, sulfitc and silica toprovide a boiler water having 405 ppm. suspended solids, 400 ppm. Palkalinity (as CflCOs) and residuals of sullitc, phosphate and silicaeach in the 25 to 80 p.p.m. zone. 2 days test.

tioning :was also better.

Run 67 shows that the same 30 p.p.m. level of treatment using the sodiumsalt of car boxymethylcellulose plus chestnut tannin was also good in'lowering total deposit but gave less turbidity than the combination ofthe #3 sodium salt of carboxymethylcel-lulose with the modified tannins.It will be noted that the modified tannins when used with the sodiumsalt of carboxymethylcellulose gave an 88% decrease in deposit on thelow heat transfer area and gave a 90% decrease in deposit on the highheat transfer area. The turbidity increase was 18 fold over the resultwhen no organic additive was used and the tunbidity was double ascompared to the test when modified tannins alone were vused.

Table 3 and FIGURES 2 and 3 show the results from feeding sodiumlignosulfonate in various concentrations as compared with sodiumcarboxymethyl'cellulose and a combination of sodiumcarboxymethylcellulose and sodium lignosulfonate. 'It will be noted thatthe combination lowers the total deposit as compared with sodiumlignosulfonate alone. The'turbidity obtained, however, was onlycomparable with that of sodium lignosulfonate alone. The curves forsodium carboxymethylcellulose in IGURES 2 and 3 show how powerful thistreatment is even at very low concentrations.

Table 3 BOILER EXPERIMENTS, CMC-l-ORGANIO Total Deposit, Gms/ft.

Av. Tur- Exp. Boiler Water Treatment, ppm. bidity as No. Low High ppm.SiOi Heat Heat Trans- Transfer fer }No organic 2. 4 7. 2 10 Sodium LiguoSulfonate 2. 6 5. 7 10 30 Sodium Ligno Sulfonatc 0.7 1. 4 38 96 SodiumLigno Sullonate 0.15 0.17 93 5 CMC 7H5 0.52 1.51 56 10 CMO 7HS 0. 30 0.29 133 30 OMC 7H8 0. 09 l]. 08 266 }5 CMC 7HS-25 Sodium Ligno 0. 51 0.7835 Sulfonate.

Conditions: No. 2 Boiler, 300 p.s.i., 2 day experiments with a. feedwater of 18 p.p.m. Ca and 9 p.p.rn. Mg (both as CaOOa) and withsufiicicnt added inorganics to give boiler balances at cycles ofconcentration of 400 p.p.m. P alkalinity, 500 ppm. M alkalinity and -80p.p.rn. each of phosphate, sulfitc and silica.

EFFECT OF DEGREE OF SUBSTITUTION ON THE POWER OF THE SODTUM SALT OFCARBOXY- METHYLCELLULOSE Using the same boiler as shown in FIGURE 1, andi boiler conditions of 15 cycles of concentration, 400 ppm. Palkalinity, and residuals of sulfite, silica and phosphate each in thezone of to 80 p.p.rn., FIGURE 4 shows the effect of the degree ofsubstitution on the total deposit from 10 ppm. of sodiumcarboxyrnethylcellulose in the boiler water. It will be evident that thebest results for high heat transfer, that is, the lowest deposit, wereobtained when the degree of substitution was 0.7. The results obtainedwhen the degree of substitution was 0.9 were reasonably close, withdouble the deposit, while the results obtained with substitutions of0.4, 1.2 and 2.0 were considerably inferior.

With the low heat transfer unit, the degree of substitution was far lessimportant as a factor, and sodium carboxymethylcelluloses with degreesof substitution of 0.7, 0.9, 1.2 and 2.0 gave values in the same rangeand sodium carboxymethylcellulose with a degree of substitution of 0.4gave results which were reasonably close. These experiments on degreesof substitution were conducted for various polymer lengths from small tolarge, that is, from 500 to 2000 anhydroglucose units, and withviscosities in 1% water solutionsvarying from 100 to 20,000 centipoises,as it is not possible at this time to obtain products with constantpolymer lengths in the various substitution experiments. The practice innum- EFFECT OF LENGTH OF POLYMER ON THE EF- PECTTVENESS OF THE SODIUMSALT OF CAR- BOXYMETHYLCELLULOSE The same boiler conditions which wereused to determine tle efiect of substitution were also used in thisstudy. The tests were carried out with a constant subsitution or" 0.7.Results are presented in Table 4. At a feed of 5 ppm, the polymer lengthas evidenced by viscosity seems to be directly related to effectivenessin low heat transfer, the lowest deposit being obtained with lowerpolymer lengths and increased deposits being obtained with longerpolymer lengths. At high heat transfer, the effect of polymer length ismore powerful at intermediate polymer lengths and less powerful at theextremities.

With a feed of 10 ppm. in the boiler water, polyme length had noapparent eliect on deposit formation, all polymer lengths givingsatisfactory deposit reduction to about the same degree. It isunderstood that Type 7L has 500 to 1000 cellulose units, Type 7M has1000 to 1500 cellulose units, and Type 7H has 1500 to 2000 celluloseunits. Type 7A is believed to have a polymerization of the same order asType 7L. The same degree of polymerization can be obtained in Series 4,Series 9 and Series 12. The size of these cellulose units indicates thatin most cases there are extremely large polymers with extremely highmolecular weights.

T able 4 EFFECT OF POLYMER LENGTH AT SUBSTITUTION 0.7

Deposit, GmJft. 0M0, Viscosity, Exp. No. ppm. Log of Trade in Sol. 25 CViscosity Low High Designation Boiler Heat Heat Water Trans- Transferfer 14 1. 146 0. 3t 3. 07 CMC 7AP 36 1. 556 0. 48 1. 25 CMO 7LP 450 2.653 1.13 1. 33 0M0 7MP 40, 000 4. 602 1.99 3.14 OMC-7HP 14 1.146 0.32 0.33 CMC 7A1 36 1. 556 0. 35 0. 32 OMC 7LP 450 2. 653 0.33 0. 42 0M0 7MP40, 000 4. 602 0.28 0.21 CMC 7HP Conditions: Experimental Boiler No. 2,300 p.s.i., 15 cycles of concentration, with a feed water of 18 ppm. Ca,9 p.p.m. Mg (both as CaCOs) and sufiicient alkalinity, phosphate, silicaand sulfite to give boiler water balances of 400 ppm. P alkalinity (asOaC O and residuals of phosphate, silica and sullite each in the 20-90ppm. zone.

EFFECTS OF HEAT TRANSFER, TEMPERATURE AND PRESSURE ON EFFECTIVENESS OFTHE SODIUM SALT oF CARBOXYMETHYLCELLU- LOSE No difiiculties have beenencountered in employing water soluble salts of carboxymethylcellulosein the form of viscous solutions with or without other organicmaterials. The sodium salt of carboxymethylcellulose can be preswelledin water with constant'stirring to provide a viscous clear product whichcan then be treated with other inorganic chemicals and wtih organicchemicals such as tannin, lignin, sulfonated lignin or thiolignin. Theproducts can be diluted at the time of use in the plants and offer verysatisfactory feed solutions for introducing the materials into theboiler system. The additives will be suitably Water soluble phosphatessuch as sodium tripolyphosphate, sodium hexametaphosphate, disodium hydrogen phosphate, monosodium dihydrogen phosphate and similar watersoluble poly and ortho phosphates; water soluble hydroxides such assodium hydroxide and potassium hydroxide; water soluble silicates, suchas Metso anhydrous silicate (Na SiO and other simple water solublemetasilicates and orthosilicates; water soluble carbonates such assodium carbonate, sodium bicarbonate; and water soluble sulfites such asodium sulfite and sodium acid sulfite which act as oxygen scavengers sothat the boiler operates in an oxygen-free system or very close to it.Other oxygen scavengers such as hydrazine can also be employed. Theorganic material such as tannins, lignins, sulfonated lignins andthiolignins are also additives. The antifoams as mentioned herein arealso suitable additives.

Powdered products containing powdered sodium carboxymethylcellulose orsodium carboxymethylcellulose in powdered form with other powderedorganic material as mentioned above are not as easy to handle in plantpreparation of feed solutions as are the pastes, but they can be usedsatisfactorily if desired.

EFFECTIVENESS OF THE SODIUM SALT OF CAR- BOXYMETHYLCELLULOSE AND THESODIUM SALT OF CARBOXYMETHYLCELLULOSE PLUS OTHER ORGANIC MATERIALS ONBOILER WA- TER FOAMING AND STEAM PURITY 'ble sodium salt ofcarboxymethylcellulose in the effective concentration zone and withother organic materials such as lignin, tannin, sulfonated lignin andthiolignin gave excellent quality of steam.

The limit of other organics such as tannins and lignins may be as highas 500 ppm. under extraordinary circumstances, and most desirably 200ppm. for moderate loads, there being an effective concentration presentin the boiler at all times, which for example on a light load might beppm.

EFFECT OF THE SODIUM SALT OF CARBOXY- METHYLCELLULOSE PLUS OTHER ORGANICMATERIALS ON REDUCING DEPOSITS OF CAL- CIUM PHOSPHATE, MAGNESIUMHYDROXIDE AND MAGNESIUM SILICATES In boilers which are operated withsuflicient water soluble phosphates such as any one of the sodiumorthophosphates, orthophosphoric acid,,or any one of the sodiummolecularly dehydrated phosphates or any of the corresponding phosphatesof potassium (and sufiicient alkalinity to insure precipitation),calcium is usually precipitated as tricalcium phosphate. Under specialconditions of alkalinity, the precipitate may be one of the apatites xCa(PO .yCa(OH) where x and vary depending on conditions. Under these sameconditions, magnesium is precipitated as the hydroxide and as one of thesilicates such as serpentine (3MgO.2SiO .2i-I O). If the feed watercontains small amounts of iron, alumi- $3 num, copper, etc., many othercompounds may be formed but these are likely to be in trace amounts.Boiler water sludges and deposits predominately contain tricalciumphosphates with the possibility of some calcium hydroxy phosphate, andmagnesium as the hydroxides and silicates.

Without going into all of the complexities of boiler water chemistry,reference is made to Table 5 which shows the behavior of sodiumcarboxymethylcellulose and sodium carboxymethylcellulose with organicmaterials in reducing the boiler precipitates or sludges which otherwisewould adhere :on heat transfer surfaces, as well as conditioning thesludges so that they are Welldispersed for blowdown from the boiler. Itthere is shown that '10 ppm. of sodium carboxymethylcellulose in theType 7HSP form reduced tricalcium phosphate expressed in terms ofcalcium by on the low heat transfer surface and on the high heattransfer surface. This same treatment reduced the mag esium by 82% onthe low heat transfer surface and 77% on the high heat transfer surface.A similar advantageous reduction was obtained in the calcium andmagnesium deposits on the low and high heat transfer surfaces by thecombination treatment of the sodium salt of carboxymethylcellulose andsodium lignosulfonate.

Table 6 shows that under different testing conditions a combination ofsodium carboxymethylcellulose and modified tannin treatment reduced thecalcium and magnesium deposit on both high and low heat transfersurfaces.

1 Occurred as Caa(P0i)2 predominately.

2 Occurred as a combination of Mg(OH): and 3MgO.2SiO predominately.

Conditions: Boiler 2, 300 psi, 15 cycles of concentration low heattransfer heater of 28,000 B.t.u. per ft. per hr., high heat transfer of180,000 B.t.u. per ft. per hr., 2 day tests. Feed water had 18 ppm. Caand 9 p.p.m. Mg (both as CaCOs), and suthcient alkalinity, sulfitc,phosphate and silica to give boiler water balances of 400 p.p.m. Palkalinity and 30-80 ppm. residual each of S03, P04 and lSiOz.

Table 6 Low Heat High Heat Transfer, Transfer, Exp Boiler Watertreatment, Guns/it). Gms/it.

No. ppm.

Ca Mg Ca Mg 71 No Organic 0. 44 0. 11 2.11 0. 26 60 7.5 CMC 7HSP-22.5Modi- 0.05 0. 02 0.12 0.08

fied Tannin gccurret as gamggah pridomiiately. V

ccurre as g i an 3M .2Si0 rcdominatel see p nniti n i; gable 2. g 2 p yon i ions: 0 oiler, 300 p.s.i., 15 cycles, 3 da testin low heat transferscaling heater 28,000 B.t.u. per it? per hr., high h at transfer scalingheater 180,000 B.t.u. per it. per hr. with a feed water containing 8 ppmCa, 3 p.p.m. lvig (both as Capos) and a sufficient alkalinity, sulfite,phosphate and silica to g ve boiler water balances of 600 ppm. Palkalinity and 30-90 p.p.m. residuals each of phosphate, silica andsulfite.

All of these experiments used excess phosphate and acceptable alkalinitylevels to keep the pH above 10.5 and preferably in the range from 11.0to 11.5 but the invention is not limited thereto. They producecarbonates and sulfates in which the carbonates and sulfates are intrace amounts only as the carbonates and sulfates are too soluble toprecipitate, and the precipitates being predominantly phosphates,hydroxides and silicates.

The other water soluble salts of carboxymethylcellulose behave the sameas the sodium salt.

In view of our invention and disclosure, variations and modifications tomeet individual whim or particular need will doubtless become evident toothers skilled in the art, to obtain all or part of the benefits of ourinvention without copying the process and composition shown, and we,therefore, claim all such insofar as they fall within the reasonablespirit and scope of our claims.

Having thus described ouriuvention what we claim as new and desire tosecure by Letters Patent is:

1. A process of reducing phosphate, hydroxide and silicate deposits insteam generating equipment having Water containing alkalinity,phosphate, silicate, an oxygen scavenger and antifoam, which comprisesintroducing into the water of the steam generating equipment between and100 ppm. of a sodium salt of carboxymethylcellulose having asubstitution of carboxymethyl groups within the range from 0.7 to 0.9,inclusive, having a polymer length of between 500 and 2000anhydroglucose units and having a viscosity in a 2% water solution ofbetween and 40,000 centipoises.

2. A process of claim 1, which comprises introducing a sodium salt ofcarboxymethylcellulose having a substitution of carboxymethyl groups of0.7.

3. A process of claim 1, which comprises introducing the sodium salt ofcarboxymethylcellulose as a powder, in combination with (1) a materialof the class consisting of a water soluble phosphate, a water solublehydroxide, a water soluble carbonate, a water soluble sulfite, and awater soluble silicate, (2) an antifoam, and (3) an organic material ofthe class consisting of tannin, lignin, sulfonated lignin andthiolignin, said powder facilitating the feeding of the sodium salt ofcarboxymethylcellulose.

4. A process of reducing phosphate, hydroxide and silicate deposits insteam generating equipment having water containing alkalinity,phosphate, silicate, an oxygen scavenger and antifoam, which comprisesintroducing into the water of the steam generating equipment between 5and 100 p.p.m. of a sodium salt of carboxymethylcellulose having asubstitution of carboxymethyl groups within the range from 0.7 to 0.9,inclusive, having a polymer length of between 500 and 2000anhydroglucose units and having a viscosity in a 2% water solution ofbetween 15 and 40,000 centipoises and also introducing into the steamgenerating equipment an organic material 10 of the class consisting oftannin, lignin, sulfonated lignin and thiolignin, and maintaining aconcentration of said organic material in the steam generating equipmentwhich is effective at all times and up to 500 ppm.

5. A process water in a steam generating equipment containing from 5 to100 ppm. of a sodium salt of carboxymethylcellulose, saidcarboxymethylcellulose having a substitution of carboxymethyl groupswithin the range from 0.7 to 0.9, inclusive, having a polymer length ofbetween 500 and 2000 anhydroglucose'units and having a viscosity in 2%water solution between 15 and 40,000 centipoises, and said process wateralso containing alkalinity, phosphate, silicate, an oxygen scavenger andantifoam.

6. A process water in a steam generating equipment containing from 5 to100 p.p.m. of a sodium salt of carboxymethylcellulose, saidcarboxymethylcellulose having a substitution of carboxymethyl groupswithin the range from 0.7 to 0.9, inclusive, having a polymer length ofbetween 500 and 2000 anhydroglucose units and having a viscosity in 2%water solution between 15 and 40,000 centipoises, and said process wateralso containing an efiective amount and up to 500 p.p.m. of an organicmaterial of a class consisting of tannin, lignin, sulfonated lignin andthiolignin, and the said process water also containing alkalinity,phosphate, silicate, an oxygen scavenger an antifoam.

References Cited by the Examiner UNITED STATES PATENTS 2,727,867 12/55Denman et a1. 2,783,200 2/57 Crum et a1. 210-56 X OTHER REFERENCESNieuwenhuis: Improvement of the Dirt suspending Power of CMC, I. PolymerSci., 12, 237-52 (1954).

Betz: Handbook of Industrial Water Conditioning, Betz Laboratories,Inc., Phila. 24, Pa., 5th ed., 1957, pp. -99, -112.

Sodium Carboxymethylcellulose, a publication of the Hercules Powder Co.,Wilmington, Del, 1944, 4 pp.

Hercules Cellulose Gum (CMC), pub. of Hercules Powder Co., 1951, 20 pp.

Hercules Cellulose Gum (CMC), pub. of Hercules Powder Co., 1949, 11 pp.

MORRIS 0. WOLK, Primary Examiner.

1. A PROCESS OF REDUCING PHOSPHATE, HYDROXIDE AND SILICATE DEPOSITS INSTEAM GENERATING EQUIPMENT HAVING WATER CONTAINING ALKALINITY,PHOSPHATE, SILICATE, AN OXYGEN SCAVENGER AND ANTIFOAM, WHICH COMPRISESINTRODUCING INTO THE WATER OF THE STEAM GENERATING EQUIPMENT BETWEEN 5AND 100 P.P.M. OF A SODIUM SALT OF CARBOXYMETHYLCELLULOSE HAVING ASTUSTITUTION OF CARBOXYMETHYL GROUPS WITHIN THE RANGE FROM 0.7 TO 0.9,INCLUSIVE, HAVING A POLYMER